The present invention relates to an apparatus and a method for automated testing of a hybrid actuator.
The term hybrid actuator relates to a combined indicator lens and potentiometer actuator as disclosed in a co-pending European Patent Application No. 00308597.4 our file number 2000P05003/EP entitled xe2x80x9cHybrid Actuatorxe2x80x9d and filed concurrently herewith. In particular, the invention relates to the automated testing of a hybrid actuator disposed in a frequency inverter supplying a variable speed motor, for example a COMBIMASTER [Registered Trademark] 411 combination motor and inverter.
Variable speed motors are used in many settings, for example for driving mechanical handling equipment, for driving electric fans or for powering conveyor belts. Rather than simply varying the voltage applied to a motor, it has been found more efficient to use frequency inverters to convert mains electricity into a variable, three phase power supply.
Variation of the speed of operation of variable speed motor can be achieved through the rotation of an external knob which engages an internal potentiometer. It is often advantageous that adjustment of the speed of operation be as simple as possible and as a result the knob can be arranged to be operable by hand or by means of a coin or a screwdriver. The rotational adjustment may also be imparted by means of a dedicated tool.
The inverter can be in a number of different operational states, for example normal operation, malfunction and test mode. To indicate the current state, the inverter may be provided with an indicator arrangement. This indicator arrangement may comprise internal indicator lamps, for example light emitting diodes (LEDs), and corresponding indicator ports in a wall of the inverter housing. The provision of an indicator arrangement reduces the need for internal access for inspection and is thus a practical safety feature.
The indicator lamps can be arranged to blink with different patterns corresponding to different operational states. Alternatively indicators may be provided which can generate signals of a variety of colours, for example red for malfunction, green for normal operation. It is possible that a single indicator can produce signals of more than one colour, for example certain light emitting diodes allow the production of light at a number of different wavelengths. Naturally other signals can be used to indicate operational states for example audible signals from a loudspeaker.
Of great importance in the reliable operation of electrical devices, inverters included, is isolation from undesirable material. Dust and water can cause particular problems and standards have evolved which detail the degree to which a device is proof against the ingress of water and dust. The environmental protection achieved by frequency inverters is graded along an index of protection (IP) wherein the protection against dust is graded along one scale and against water on another scale, for example an IP rating IP56 corresponds to 5 on the dust scale (ranging from no protectionxe2x80x940 to total protectionxe2x80x946) and 6 on the water scale (ranging from no protectionxe2x80x940 to protection against continuous submersionxe2x80x948).
For each indicator port and potentiometer adjustment knob port in an inverter""s housing the index of protection for the whole inverter is marginally more compromised. If the number of possible ingress points can be reduced a higher IP rating can be attained. In the co-pending European Patent Application No. 00308597.4 discussed above (Attorney Docket Number 2000P05003/EP), there is disclosed an inverter having a single ingress point for a hybrid actuator. The hybrid actuator can be rotated to impart an adjustment upon a potentiometer. Furthermore the hybrid actuator is made of a transparent material to allow the light from an internal indicator lamp to be visible through the single ingress point.
The hybrid actuator can be tested manually by turning the actuator to a number of predetermined positions and confirming that the inverter performs satisfactorily. The manual test then requires that the indicator arrangement be inspected to ensure that the various possible states of the inverter are correctly displayed through the lensing function of the hybrid actuator. Finally the manual test must ensure that the hybrid actuator is returned to a minimum potentiometer setting to avoid damage when the inverter is first used.
Manual testing is performed by a production operative. The production operative often has many other tasks apart from testing. The drawbacks of manual testing thus include: human error; inconsistent testing criteria; added time overheads (for both the production operative performing the test and for the additional time the inverter is in production); and interruption of other non-testing tasks.
The present invention seeks to overcome the problems arising in the testing of hybrid actuators.
In accordance with one aspect of the present invention, there is provided a testing apparatus for testing an electrical device comprising: a housing; a rotatable control means; an indicator arrangement; and a hybrid actuator, the hybrid actuator being substantially transparent to allow light from the indicator arrangement to be observed from outside the housing, the hybrid actuator being operable to engage with the rotatable control means and whereby to enable rotation about an axis; characterised in that the test apparatus includes: a rotatable test head which has an engaging portion for engaging a head portion of said hybrid actuator; a light sensing means; a processing means for receiving sensed light data from the light sensing means, for receiving performance data from the electrical device and for controlling the movement of the rotatable test head; and a drive means for driving the rotatable test head about the axis in accordance with a control signal generated by the processing means. It is preferred that the light sensing means is provided upon the rotatable test head.
A light sensing means may be provided either on the rotatable test head or close enough to the rotatable test head to be able to monitor light emitted by the hybrid actuator. In one possible arrangement the light sensing means may be provided behind the rotatable test head and the rotatable test head may be substantially transparent thereby allowing light to penetrate through to the light sensing means. In another possible arrangement, the light sensing means is disposed in a non-rotating axial portion of the rotatable test head and a remaining radial portion of the rotatable test head rotates about the axial portion.
Preferably, the engaging portion of the rotatable test head engages with a corresponding receiving recess provided on the head portion and thereby aligns the light sensing means with the hybrid actuator.
The light sensing means advantageously monitors light emitted by the indicator arrangement.
In a preferred embodiment, the electrical device is an inverter, the rotatable control means is a potentiometer and the indicator arrangement is a light emitting diode. Here the performance data received from the inverter may be a sample of the output voltage of the inverter.
Automated testing of the hybrid actuator gives a great improvement over manual testing since a high level of quality can be maintained with the minimum of additional testing time and production operative attention.
In a further aspect of the present invention there is provided a method for testing an electrical device comprising: a housing; a rotatable control means; an indicator arrangement; and a hybrid actuator, the hybrid actuator being substantially transparent to allow light from the indicator arrangement to be observed from outside the housing, engaging with the rotatable control means and rotating about an axis; the method characterised by the steps of: providing a test apparatus which includes: a rotatable test head; a light sensing means; a drive means; and a processing means for controlling the movement of the rotatable test head; engaging the rotatable test head with a head portion of the hybrid actuator; driving the rotatable test head about the axis into a plurality of different testing positions in accordance with a control signal generated by the processing means; in each of the different testing positions, monitoring performance data for the electrical device; monitoring the light emanating from the hybrid actuator, the light sensing means sensing the light emanating from the hybrid actuator and generating sensed light data; and receiving and processing the sensed light data and the performance data and generating a report of the received data.